1. Field of the Invention
The present invention relates to a transportation control system or a system for controlling physical distribution pallets used in wide area physical distribution, and in particular to a system for controlling physical distribution pallets, by which it is possible to adjust arrangement of pallets at each physical distribution base to facilitate smooth physical distribution and to set up a forwarding plan to match the reality or to provide detailed control information.
2. Description of the Related Art
To control mobile objects or articles in facilities, a technique has been known in the past, in which a transponding card, i.e. an IC card provided with wireless transmission and receiving functions is mounted on the mobile object or the article, and information such as position information issued by the transponding card is collected at a center to identify the position of the mobile object or the presence of the object (Japanese Patent Publications 5-35934 and 5-67091).
Also, as the technique relating to setting-up of forwarding plan of transport container, the methods have been proposed for distribution plan of sea-borne containers "Imai, A. et al.: "A Study on the Short Period Planning for the Distribution of Empty Sea-borne Containers", Navigation Association of Japan, No. 81, pp. 1-8, 1989) or for the forwarding plan of railroad containers (Fukumura, N.: Planning for Forwarding of Empty Containers, Using a Mathematical Programming Method", RTRI Report, Vol. 8, No. 2, pp. 39-44, 1992).
For pallets, which are transport containers in wide area distribution, it is necessary for maintaining smooth physical distribution to identify quantity of pallets in stock at each physical distribution base and to keep sufficient quantity of pallets to match the transport quantity of the articles. At present, stock control of this type of pallets is carried out by human power.
On the other hand, various types of systems to set up transport planning of freight and containers have been conceived under computer-aided design. A system for setting up transport planning through interactive transaction with users is proposed in Japanese Patent Publication Laid-Open 62-1070. Japanese Patent Publication Laid-Open 6-259411 discloses a system of agent model, in which a plurality of processing modules are provided to set up transport planning of objects to be transported in each transport medium, and transport schedule is prepared through information exchange between the modules.
In the physical distribution field, a new mode of freight transportation is increasingly introduced in recent years, which uses pallets to facilitate the execution of loading and unloading operation. The pallets are carried to various places all over the country with cargoes placed on them. After unloading the cargoes, the pallets are sent to the other places with new cargoes placed on them. However, freight transportation is usually one-way transportation from a place of supply to a place of demand, and good balance is not always kept in transportation quantity between these areas. As a result, there are a lot of empty pallets stagnated at a distribution base, while pallets for loading cargoes are in shortage in another distribution base. For this reason, it is necessary to constantly control the stock of pallets and to send empty pallets from an area where pallets are in excess to an area where pallets are in shortage.
The sending of empty pallets may be too late if it is carried out after finding out that pallets are in shortage. The needed quantity of pallets must be transported in advance. It is necessary to predict freight transport quantity at each physical distribution base so that no inconvenience or trouble occurs in freight transportation. Also, the best route of transportation must be selected to reduce the cost for such transportation.
There are the following references discussing the transportation of containers and pallets: Kojima, K. et al.: "The Building of a Simulation System for Prediction of the Number of Necessary Pallets", Kato, S. et al.: "A Study on Pallet Transportation Problem" (50th National Conference of Information Processing Society), or Fukumura: "Planning the Forwarding of Empty Containers, Using a Mathematical Programming Method", (RTRI Report, Vol. 8, No. 2, February 1994). In the last reference, description is given on a technique to plan the forwarding of empty containers, based on a mathematical programming method using model.
In the conventional methods, however, it is not possible to solve the problems related to the control of pallets in wide area physical distribution as described below. In the wide area physical distribution, there are tremendous quantity of pallets in distribution, and it is also very difficult to uniformly perform stock control of these pallets at high accuracy because the pallets are to be distributed all over the country.
Even if a pallet is present, it cannot be utilized immediately for transportation of freight unless it is empty. In the conventional method, it is not possible to automatically identify whether the pallets are empty or not. In wide area physical distribution, it is difficult to accurately predict supply and demand of pallets used for transportation. This is because the forwarding business is to forward freight at the request of each customer, and it is difficult to predict the quantity of freight to be forwarded. The differences in areas or seasonal variations also exert extensive influence on supply and demand of pallets.
When a number of empty pallets are present far away from an area where pallets are wanted, it is necessary to forward the empty pallets and to optimize the arrangement of pallets at each distribution base, but it takes high cost for forwarding because the range of forwarding covers the whole country. It is an important problem to set up a forwarding plan to minimize the forwarding cost. The forwarding of empty pallets may be too late if it is carried out after finding out that the empty pallets are in shortage. It is also important which route of transportation should be used to optimize the forwarding of empty pallets to the destination.
When it is actually attempted to set up a plan for forwarding empty pallets, such plan must be considered in view of distribution bases all over the country. Unlike the case where a model is used, the scale of calculation is very extensive, and the time of calculation also increases.
In the pallet control as it is carried out, very elaborate control is required, i.e. to accurately identify actual status of pallets, and to estimate demand on pallets in very short time span. Based on the results, the schedule of forwarding or the time of departure and arrival must be set up, or adequate standard for pallets in stock must be determined. To set up the plan to forward pallets, full consideration must be given on the mode of transportation of the distribution or on forwarding companies and customs and practice in the forwarding business.